[media] gspca: fix dev_open() error path

If v4l2_fh_open() fails in dev_open(), gspca_dev->module left locked.
The patch adds module_put(gspca_dev->module) on this path.
Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/gspca/gspca.c

@@ -1266,6 +1266,7 @@ static void gspca_release(struct v4l2_device *v4l2_device)
 static int dev_open(struct file *file)
 {
 	struct gspca_dev *gspca_dev = video_drvdata(file);
+	int ret;
 
 	PDEBUG(D_STREAM, "[%s] open", current->comm);
 
@@ -1273,7 +1274,10 @@ static int dev_open(struct file *file)
 	if (!try_module_get(gspca_dev->module))
 		return -ENODEV;
 
-	return v4l2_fh_open(file);
+	ret = v4l2_fh_open(file);
+	if (ret)
+		module_put(gspca_dev->module);
+	return ret;
 }
 
 static int dev_close(struct file *file)